The inventive concepts described herein relate to a nonvolatile memory device, and more particularly, relate to a current generator of a nonvolatile memory device such as a resistive random access memory device and a write and/or read current calibrating method.
A magnetic random access memory (hereinafter, referred to as MRAM) may be a memory device that stores data using a resistance variation of a magnetic tunneling junction (hereinafter, referred to as MTJ) element of a memory cell. A resistance value of the MTJ element may vary according to a magnetization direction of a free layer. For example, when a magnetization direction of the free layer is parallel with that of a fixed layer, the MTJ element may have a relatively small resistance value. When a magnetization direction of the free layer is anti-parallel with that of the fixed layer, the MTJ element may have a relatively large resistance value. A relatively small resistance value of the MTJ element may correspond to data ‘0’ and a relatively large resistance value may correspond to data ‘1’.
The MRAM may write data using a data writing method in which data is written at the MTJ element using a digit line. In the MRAM employing such a write manner, a current may be applied to a digit line spaced apart from the MTJ element to generate a magnetic field, and a magnetization direction of the free layer may be changed by the magnetic field. A read current may be applied between both ends of the MTJ element. In the MRAM, a read current path may be different from a write current path. However, in a spin transfer torque magnetic random access memory (hereinafter, referred to as STT-MRAM) not employing a digit line, a read current path may be equal to a write current path. For this reason, fine control on read and write currents would be desirable.